Use cotton-tipped applicators to obtain samples from exudative or purulent areas such as ears, skin folds, and interdigital
spaces where it is difficult to lay a microscope slide flat.
EXAMINING THE SAMPLE
Scan the slide under low power using the 4X or 10X objective initially to identify the optimal location and cell types to
examine with the higher-power 40X or 100X objective. Select sites where you find inflammatory or neoplastic cells under low
power, and then examine them by using the higher-power objectives to evaluate cellular morphology or atypia and assess whether
microbes are present. The oil immersion objective is preferred over the 40X objective, as microbes are more commonly missed
under 40X magnification. If the microbes are intracellular, they are pathogens and indicate a true infection. Microbes without
inflammatory cells may indicate nonpathogenic bacteria or bacterial overgrowth. If atypical cells are seen, a skin biopsy
Cytologic examination is best performed with the light condenser up (Köhler illumination). However, when examining skin scrape
samples or unstained acetate tape preparations, keep the condenser down to create better contrast to help you identify parasites,
fungal spores, hyphae, and hair shaft abnormalities.
Cytologic examination is the most commonly used diagnostic test in dermatology practice because it is highly informative.
It is valuable when patients initially present and helps monitor their response to therapy and may indicate when an infectious
or inflammatory condition changes. The techniques are inexpensive, and interpretation is easily self-taught. If cytologic
examination becomes a part of everyday practice, additional diagnostic testing and treatment become more proficient and case
management is immediately more rewarding, resulting in happier clients and healthier patients.
Wayne Rosenkrantz, DVM, DACVD, Animal Dermatology Clinic, 2965 Edinger Ave., Tustin, CA 92780.